ALSA device labels

When you issue commands such as aplay or arecord, the commands may
need to be told which ALSA devices you want them to use.

Example:

If your sound card has two devices to play back sound (say, one analog
for your PC speakers, and another digital, using an
S/PDIF connection to your stereo), aplay will
probably default to using the analog device. If you want it to use the
digital device, you'll need to tell it to do so.

An ALSA device label generally looks something like hw:0,0 for the
first hardware PCM device, default:0 for the device configured as the
default (which in a vanilla 1.0.11 configuration is a
dmix'ed version of hw:0,0, etc.).

You can get a list of all available playback pcm devices along with
their definitions by using the command